Building construction

ABSTRACT

The invention is concerned with building construction incorporating a sealing element for use in cavity walls of buildings. The element is in the form of a strip of corrosionresistant liquid impermeable material (preferably extruded plastics). It has a part which is adapted to receive fixing means (e.g. nails) for securing the element to the stile, head or sill of a window, and two laterally spaced walls capable of entering the wall of a building. At least one part of the element also has means such as a longitudinal groove for fastening the element to the wall.

United States Patent Molyneux 1 Dec. 2, 1975 [54] BUILDING CONSTRUCTION FOREIGN PATENTS OR APPLICATIONS 1 1 lnvemorl George Molyneux 1, Hfllstead w 989,285 4/1965 United Kingdom 1 52/212 rr w Nelson, County of 1,965,465 12/1969 Germany 52/204 Lancaster, England 1,175,231 12/1969 United Kingdom 52/204 [22] Filed Aug 13 1973 124,271 5/1947 Australia 52/204 [21] Appl. No.: 387,634 Primary Examiner-Ernest R. Purser Assistant ExaminerCarl D. Friedman Related Application Data Attorney, Agent, or Firm-Norris & Bateman [62] Division of Ser. No. 120,990, March 4, 1971,

b' d d. a I 57 ABSTRACT [30] Foreign Application Prio it Data The invention is concerned with building construction Mm 24 1970 United Kingdom H 1451/70 incorporating a sealing element for use in cavity walls I of buildings. The element is in the form of a strip of 52 us. (:1. 52/204; 52/62; 52/566 Corrosion-resistant liquid impermeable material (Pref- 51 Int. c1. E06B 1/26 ably Plasticsl It has 11 which is 158] Field Of Search 52/213, 396. 466, 468, adapted to receive fixing means nails) 52/60 61 62 566, 470 471, 204 412, 216, ing the element to the stile, head or sill of a window, 7124151 2] l, 212 and two laterally spaced walls capable of entering the wall of a building. At least one part of the element [56} References Cited also has means such as a longitudinal groove for fas- UNITED STATES PATENTS Thom 52/396 X tening the element to the wall.

13 Claims, 6 Drawing Figures US. Patent Dec. 2, 1975 Sheet 2 of5 3,922,826

Y R A N MQ U.S. Patent Dec. 2, 1975 Sheet 4 of5 3,922,826

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17/1402" 74 7Z2 72fl 79 6 INVENTOR GE-ORGE MOLYNEUX US. Patent Dec. 2, 1975 Sheet 5 of 5 3,922,826

5 9. 6. 2& J

GEORGE MOLYNEUX BY x NORRIS & BATEMAN BUILDING CONSTRUCTION This is a division of copending application Ser. No. 120,990 filed Mar. 4, l97l for Building Construction and Elements For Use Therein now abandoned.

In my U.S. Pat. No. 3,707,815 there is described a building element for use at the ends of a wall which abut the sides of a door or window frame comprising a strip of water-resistant liquid-impermeable material adapted to receive fixing means for securing the element to the stile, head or sill of a door or window, and having at least a portion which is capable of entering the wall, this portion providing means for securing the element to the wall.

According to this invention a novel building construction comprises a sealer element in the form of a strip of corrosion-resistant liquid-impermeable material having a part adapted to receive fixing means for securing the element to the stile, head or sill of a door or window, and two laterally spaced walls capable of entering the wall, at least one part of the element providing means for securing the element to the wall.

Preferably the element is recessed along its length to provide a mortar and/or tie bar key. This recess may be formed in one of the laterally spaced walls, or in the part of the element which receives the fixing means for the stile, head or sill, or there may be recesses in both the laterally spaced walls or in one of these walls and the part which receives the fixing means.

The present invention therefore provides further construction in accordance with the basic concept of said Patent, and such construction incorporating several sealer elements will now be described by way of examples only with reference to the accompanying drawings, in which:

FIG. 1 is a horizontal cross-section through the end of a cavity wall showing one element and its method of use with a timber window or door frame;

FIG. 2 is a view similar to FIG. 1, but showing an alternative element;

FIG. 3 is another view similar to FIG. 1, showing another alternative element;

FIG. 4 is a cross-section through a lintel for a door or window opening;

FIG. 5 is another view similar to FIG. 1, but showing an element used with a metal window frame; and

FIG. 6 is a cross-section through a further element for use with a metal window frame.

Referring firstly to FIG. 1 of the drawings there is shown an inner leaf 330 and an outer leaf 332 of a brick-work cavity wall, with a cavity 334 between them. The two leaves 330 and 332 are tied together by conventional tie bars (not shown) except at the end portions aadjacent to an opening for a window or door frame as illustrated. 338 is the stile at one end of a window frame (which is made in wood) and in the conventional construction, the stile would abut the end of the wall, but the cavity (usually 2 inches wide) would be closed for example by alternative courses of (a) threequarter bricks laid on the inside leaf or, very rarely, on the outside leaf and (b) quarter bricks laid in the end of the cavity on the threequarter brick below it as described with reference to FIGS. 1 and 2 of said patent.

It will be noted that in the present construction, there are no bricks (threequarter or quarter) across the end 2 of the cavity, but instead, there is a special cavity end sealer 336 fitted across the end of the cavity 334.

The sealer 336 is made as an extruded section in a plastics material, such that it is substantially rigid-although some flexibility would be permissible water resistant and water impermeable. It is also desirable that the sealer should be capable of retaining these characteristics more or less permanently, and certainly for long periods, without protective coating. It should be understood however that a sealer made of other than plastics materials (e.g. metal) and coated with an adaquate layer of plastics would be within the scope of the invention.

Polyethylene or polyvinylchloride are suitable substances for the manufacture of the sealer.

It is also to be noted that the sealer 336 is of constant cross-section throughout its length. This enables it to be produced by an extrusion process, which makes the production of large quantities relatively cheap, and it also enables the sealer to be supplied in long lengths for cutting into the lengths required on any particular job.

It is a special advantage of the sealer shown herein in FIG. 1 over the various sealers described in detail in the said Patent, that the sealer 336 is of smaller total crosssectional area, so that it requires a smaller volume of plastics material per unit length than such sealers.

The shape of the sealer provides it with a channel portion 340 with parallel side walls 342 and 344 and an outer end wall 346 bridging the side walls 342 and 344. A forwardly extending flange 348 has oppositely facing dovetail-shaped recesses 350 and 352 which extend throughout the length of the sealer. It will be observed that the outer face of the channel portion 340 is beyond the outer face of the flange 348, so that a location shoulder 354 is formed on the sealer. The front side wall 342 extends inwardly of the flange 348, and has a lip 356 at its inner end so that when the sealer is fitted, it locates on the outer end face and inside face of the outer leaf 332, leaving a space 358 around the inside,

end corner of the outer leaf.

The side wall 344 is longer than the opposite side wall 342, and is formed with a rearwardly facing dovetail shaped recess 360 near to its extremity. Projecting on the rear of the side wall 344 are two parallel lips 362 and 364. The lip 362 is in extension of the wall 346 and tapers to an edge, whilst the lip 364 provides a shoulder for engagement on the front end corner of the inner leaf 330.

Finally, a series of grooves 366 is formed on the inside of the side wall 342 and the end wall 346 to act as moisture traps. Special plastics wall ties 368 are provided for use with the sealer strip 336. These ties are made as described in the said patent with dovetailshaped roots 370, and it has been found that if a small slit 372 is formed in the root of each tie, that enables the root to be compressed slightly in fitting into the dovetail recesses of the sealer. Consequently, the manufacturing tolerance on the width of the root can be increased.

When using the sealer 336, a length of sealer is cut off equal in length to the overall height of the window frame. This length is placed against the outside of the stile 338, and it is secured thereto by nails 374 driven through the flange 348. It has been found that using a suitable grade of plastics material for the sealer, it is guide easy to drive nails through the flanges for securing purposes. As described in said patent, other methods of securing could be used, for example holes could be preformed in the flanges to accept fixing screws, but this would entail forming the holes after exxtrusion which would add to the cost of the sealer. Again, it might be possible to secure the sealer to the stile by an adhesive, but whatever method is adopted, it will be apparent that the sealer must have a flange or equivalent means to receive fixing means for securing the sealer to the stile.

During the construction of the building, the window frame is placed in the required upright position resting on the conventional sill (not shown) and with the sealer located on the end corners of the first course of the leaves 330 and 332 as shown. Then the leaves 330 and 332 of the cavity wall are built up adjacent to the window frame, and the channel portion 340 of the sealer 336 will be sandwiched between the leaves. As the wall rises, mortar squeezed out from between the bricks will flow into the recesses 350 and 358 of the flange 348 (so that the heads of the nails 374 will be completely sealed). Furthermore, some mortar will flow into the dovetail recess 360, and these mortar keys have the important effect of forming a key between the two leaves 330 and 332 and the sealer 336. This not only holds the sealer firmly in position, but it also acts to tie the two wall leaves together. Whilst there will normally be a sufficient quantity of mortar squeezed out of the leaves, the bricklayer may place extra mortar between the courses in the area of the sealer to ensure that a good bond is obtained.

To increase the adhesion between the sealer 336 and the wall leaves, the tie bars 368 are inserted as and where desired, the roots of these bars being engaged in the dovetail recesses 350 and 360. The tie bar which engages in the recess 350 extends longitudinally into the end of the outer leaf 332, but the other tie bar extends laterally into the inner leaf 330. One of the advantages of the extruded section of the sealer is that the bars can be placed anywhere along its length, so that the courses in the two leaves 330 and 332 do not need to be level with each other. i

The window frame is fixed in position when the walls are built up and requires no further attention. Plaster 376 is applied to the inside reveal up to the window frame, and mastic 74 can be applied to the outside in the shadow line recess 378 in the usual way. It will be observed that the mastic seal is not so vital when using the inventioin as it is in the conventional construction, because the sealer itself acts to prevent ingress of water. The flange 348 ensures that the frame is spaced from the brickwork which of course, helps to keep the timber stile dry and there is a recess 352 formed behind the stile, which is useful, because it allows moisture in the timber stile to dry out, which is not always possible with known methods of fixing the window frame.

It will be clear that the impervious nature of the sealer 336 ensures that there is a proper damp proof course between the inner and outer leaves of the cavity wall at the critical area near to the window opening. Moisture cannot creep around the sealer because of the grooves 366, which act as moisture traps, nor can it cross the gap 352 if it should attempt to flow by capilliary action between the flange 348 and the stile 338. Another important feature is that because of its extension throughout the height of the stile between the sill and the lintel, it is not possible for mortar to fall on to it and bridge the cavity. It isparticularly worthy of note that the frame cannot get out of true during the building and does not require adjustment after the mortar is set.

The sealer illustrated in FIG. 1 allows the window frame to be fitted on the outside leaf 332 of the wall.

The face of the end wall 346 which is exposed inside the building is level with the plaster and can be decorated at the same time as the plaster.

The alternative form of sealer 400 illustrated in FIG. 2 of the drawings is somewhat similar to some of the sealers described in said patent, and it will be observed that this sealer is adapted to secure the stile 402 of a window frame in a central position where it bridges the cavity 404 between inner and outer leaves 406 and 408 of the cavity wall.-

In common with the sealers described in said Patent, the sealer 400 has a deep channel-shaped portion 410 which is capable of entering the cavity 404, a pair of flanges 412 and 414 which are intended to engage with the stile 402, and the end wall 416 of the channel-portion 410 has moisture trap grooves 418. The flanges 412 and 414 have lips 420 and 422 respectively for 10- cating against the end of the cavity wall, and these ensure that the stile 402 is spaced from the brickwork, and also provides a shadow line at the outside to receive mastic. An outwardly directed lip 424 on the flange 414 provides a location for the inside face of the stile 402, and enables nails 426 to be driven into the stile at right angles to nails 428 driven through the flange 412. At the extremity of the lip 424, there is a lip 430 which acts as a ground for a plasterers trowel when plaster 432 is applied.

The side walls 434 and 436 of the channel portion 410 are different from those described in said patent in that each wall comprises portions 438 which diverge from the flange end and portions 440 which converge towards the end wall 416. The dovetail recesses 442 and 444 for the tie bars 446 are formed in the portions 440, and it will be noted that the portions 438 extend far enough to form one wall of each dovetail recess, and these extensions also serve to locate the channel portion 410 in the cavity 404.

In FIG. 3, there is illustrated a sealer 500, which is very similar to the sealer 336 illustrated in FIG. 1, and apart from the differences described below, the sealer 500 is identical in all respects with the sealer 336.

Firstly, the web 502, which bridges the cavity 504 between the outer leaf 506 and inner leaf 508 of the wall, is not spaced from the end of the wall as is the web 346, but has a short extension lip 510, which rests against the end of the inner leaf 508. Also, the web 502 is arranged so that its inside face is approximately in line with the inside face of the outer flange 512 (which is identical with the flange 348 of FIG. 1).

The sealer 500 has laterally spaced walls 514 and 516 which are similar to the walls 342 and 344, but in this instance the wall 514 has a short outer extension 518 terminating in an inwardly directed lip 520. The outside face of the web 502 is covered key small square protrusions 522 which serve as a ey for plaster. When the sealer is being extruded it is only possible to form longitudinally extending ribs on the face of the web, but subsequently, whilst the extrusion is still in a plastic state, it is subjected to the action of a ribbed roller, which impresses lateral grooves into the ribbed face, thus dividing the ribs into square protrusions.

When the sealer (attached to its window frame) is fitted in the building, the flange 512 and the lip 510 abut against the ends of the outer and inner leaves 506 and 508 respectively, and the walls 514 and 516 abut against the inside (cavity) faces of these leaves. The web 502 is then across the end of the cavity, and plaster 522 can be applied on the inside leaf, using the face of the lip 520 as a guide for the plasterers trowel. The plaster is keyed on to the protrusions 522, and its end is held between the web 502 and the lip 520.

One of the advantages of the sealer 500 over the sealer 336 is that very little of the sealer 500 (in practice only the face of the lip 520) will be visible inside the building. Another advantage is the keying of the plaster to the web 502.

It should be understood that other methods of keying the plaster may be used. For example, it may be sufficient to provide only longitudinal ribs on the face of the webs, in which case the additional rolling process is not required or lateral ribs may be used without longitudinal grooving. Or, instead of protrusions on the face of the web, there could be a dovetail recess similar to those used on other parts of the sealer.

If the sealer is to be used in a building where only the outside leaf is made of bricks or the like and the inside leaf is a clad timber frame, then it will not be necessary to provide a dovetail tie bar recess in the inner wall 516 of the sealer. Instead, the inner wall 516 will be simply nailed to the inner leaf before the outer leaf is built up, and the only tie bars will be those in the flange 512 extending into the outer leaf 506.

FIG. 3 also illustrates a slightly modified tie bar 530 wherein the root portion retains its dovetail exterior, but is formed by two diverging teeth 532 with a relatively large V-shaped gap 534 between them. This construction allows the roots to be made oversize in relation to the recesses they have to fit into, so that the root portion is compressed in use to tighten its grip in the sealer.

Turning now to FIG. 4, there is illustrated an element 600, which provides a lintel over the top of a door or window opening. As in the previous examples, this element is made as an extrusion in plastics material, such as rigid polyvinylchloride, and consequent upon its method of manufacture, it is of constant cross-section throughout its length.

The lintel element can be made in long lengths and cut to the correct length for any particular job, but in this case, it should be mentioned that there may be practical limits to the length which can be used because the element does to some extent act as a load bearer in the building construction. However, tests carried out so far show that the lintel has surprisingly good load-bearing qualities and therefore it may prove possible to use it for all normal building purpose.

It will be observed that the left hand part of the element (as seen in FIG. 4) is identical with the element shown in FIG. 3 of said patent. That is to say, that it has a channel portion 602 which is adapted to enter the cavity between inner and outer leaves ofa wall, and the side walls of the channel 602 have dovetail-shaped recesses 604 throughout their length to act as mortar keys and to provide anchorages for tie bars 606.

At one side there is a short flange 608 which provides a means of nailing or screwing the element to part of a timber frame, and this is similar to the flanges provided at both sides of the channel portion in the sealer described in said Patent. However, on the side of the sealer which is to be on the outside when in the building, there is a wide flange 610, which is adapted to extend to across the greater part ofthe width ofa building block or brick. The flange 610, may for example, be

about 3 inches wide.

As shown in FIG. 4, there are three dovetail-shaped recesses 612 of the type provided on all the elements in accordance with the invention along the inside face of the wide flange 610. A special tie plate 614 is provided for use with this lintel element (in practice a series of these tie plates will be fitted at spaced intervals along the length of the lintel). As illustrated in FIG. 4, the tie plate has five sides and is adapted to bridge the carrier between one of the walls of the channelportion 604 and the wide flange 610. Two dovetail-shaped tongues 616 are formed on each of two of the edges of the tie plate to engage in four of the grooves as shown, so tying the flange 610 to the channel portion 604. The tongues may be formed in the same manner as the roots of the tie bars illustrated in FIGS. 1 to 3, but as there are four tongues to each plate 614, it may be necessary to fit all the plates by sliding them along the lintel from one end.

To use the lintel element, a length is cut adequate to extend along the length of the top frame member or head of a timber door or window frame (and long enough to extend beyond the sides of this head to cover sealing strips fitted to the jambs of the frame). This length is then secured to the head by nails or screws as described with reference to the preceding examples herein. In all probability similar sealing elements in accordance with the invention will be fitted to the jambs of the frame and therefore the wall is built up with the frame in situ, and the channel portions of the jamb sealers in the cavities of the wall. This ensures that the channel portion 604 of the lintel will be aligned with the cavity above the frame.

When the part of the wall above the door or window is being constructed, the outside leaf of the wall is supported by the flange 610 which thus replaces the usual angle iron support. At intervals between the bricks of the first course, which rests directly on the flange 610, the tie plates 614 are inserted and this helps to hold the flange 610 in the correct horizontal position to support the outside leaf over the window. The channel portion 604 is of course, held to the inside leaf by the tie bars 606.

I-Ioles 618 are formed in the plate 614 and the mortar buttered on to the end of brick enters these holes and helps to secure the plate and therefore helps to hold the flange 610 horizontal.

The sealer element 700 shown in FIG. 5 is intended to be used with a metal window or door frame. In said Patent two sealers are specifically described for use with metal frames, but these suffer from the disadvantage that they require the use of special timber inserts. On the contrary, the sealer 700 can be used without any such insert.

As with the sealers described above with reference to FIGS. 1 and 3 of the drawings, there is a web 702 which is intended to bridge a cavity.704 between inner and outer leaves 706 and 708 of a cavity wall. Also there is a pairof laterally spaced walls 710 and 712 which extend from the web 702, so forming a channel portion for entry into the cavity. The walls 710 and 712 abut against the inside faces of the leaves 708 and 706, and each is formed with a longitudinally extending dovetail recess 714 to receive the special tie bars 716 as in previous examples. In this particular instance the walls 710 and 712 are identical, but it will be understood that they could be similar to the walls of the sealer 336 for example.

The web 702 has short extensions 718 and 720 beyond the walls 710 and 712 to locate against the ends of the leaves 708 and 706 as shown, and a central dovetail recess portion 722 open on the outside. Moisture trap grooves 724 of the type described with reference to earlier examples are formed on the inside face of the web 702.

The wall 710 extends a short distance on the outside of the web 702, and carries an inturned flange 726.

There is shown at 730 part of a side member of a metal window frame. This member 730 is drilled at intervals to receive countersunk headed bolts 732 as shown. The frame is placed against the flange 726, and at each position where there is a hole for a bolt 732 in the metal frame, a corresponding hole is drilled or punched in the flange 726.The bolts 732 are then fitted and it is possible to apply nuts 734 to the bolts on the inside of the flange 726 to secure the sealer 700 to the metal frame. As indicated, there may be small ribs 718 which engage with flats on opposite sides of the nut 734, so that tightening has to be effected by turning the bolt.

The wall is then built up with the frame in situ as in previous examples, and finally plaster 736 is applied and is keyed into the dovetail recess 722 and held by the flange 726. The sealer then functions as in previous examples.

The sealer 800 shown in FIG. 6 is identical with that shown in FIG. 5, excepting that it has a relatively wide flange 802 parallel with its web 804. This flange 802 receives a thicker type of window frame 806, and the sealers 700 and 800 illustrate ways in which the actual shape of certain parts of the sealers can be varied to suit different types of window or door frame.

Sealing elements as described herein may be fixed together to form a complete sub-frame for a window. It should also be understood that the invention includes a method of building which utilizes a sealing element in accordance with the invention.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

l. A structural assembly comprising a pair of walls, each wall having inner and outer leaves, each of said leaves being built-up from a plurality of building blocks bonded together by cementitious material, and said leaves being laterally spaced from each other to provide a cavity therebetween; a frame having sides and being positioned with its sides in close juxtaposition to ends of said walls, and damp proof course elements positioned at least between said frame sides and said ends of said walls, each of said damp proof course elements comprising an integral strip of plastics material along its frame side with corrosion-resistant, liquid-impermeable properties, each strip being of constant cross-section throughout its length, each strip having a first longitudinal part and a second longitudinal part, said first part of said each strip engaging between its frame side and at least one of said leaves of its wall end, said second part of said each strip bridging the end of said cav- 8 ity between said leaves of its wall end, said each strip further having a cavity entering part comprising a pair of laterally spaced walls extending into said cavity, and keying means securing said elements to said walls.

2. A structural assembly according to claim 1 wherein at least one longitudinal portion of each of said damp proof course elements adjacent its wall has an undercut recess along its length facing its wall to provide said keying means for securing said each element to its wall.

3. A structural assembly according to claim 1, wherein each said part of said damp proof element engaging between said frame side and said wall is pierced by fixing devices securing said damp proof element to said frame.

4. A structural assembly according to claim 1, wherein a recess is formed in each said damp proof course element along the length of said part of said damp proof element engaging between said frame side and said wall to provide a keying formation for securing said element to said wall.

5. A structural assembly according to claim 4, wherein said longitudinally extending recess is dovetail shaped in cross-section.

6. A structural assembly according to claim 1, wherein a recess is formed in each said damp proof course element along the length of at least one of said laterally spaced walls thereof to provide a keying formation for securing said element to said wall.

7. A structural assembly according to claim 6, wherein said longitudinally extending recess is dovetail shaped in cross-section.

8. A structural assembly according to claim 1, wherein said bridging part is connected at opposite ends to adjacent ends of said laterally spaced walls, and the other ends of said laterally spaced walls are spaced to define with said bridging part a substantially U- shaped intermediate configuration in said strip.

9. A structural assembly according to claim 1, wherein said damp proof course elements are extruded strips.

10. A structural assembly according to claim 1, wherein said first part of each strip comprises a first flange extending along one side edge of the strip in sealing disposition between said frame and the outer end of said one leaf, said second part of said strip comprises a web laterally bridging the end of the cavity between said leaves, and said cavity entering part comprises a pair of laterally spaced walls projecting in the same direction from said web and extending into said cavity and a second flange extending along the other side of said strip sealingly engaging the outer end of the other of said leaves.

11. The structural assembly defined in claim 10, wherein one of said laterally spaced walls is formed with an undercut recess to provide anchorages for detachable wall ties at any position along the length of said strip.

12. The structural assembly defined in claim 10, wherein said first flange and said web are substantially parallel and said first flange is formed with oppositely facing longitudinal recesses, one recess opening in the same direction that said laterally spaced walls project and the other opening toward the frame engaging side.

13. The structural assembly defined in claim 10, wherein said web is formed on the side facing the interior of said cavity with moisture trap grooves. 

1. A structural assembly comprising a pair of walls, each wall having inner and outer leaves, each of said leaves being built-up from a plurality of building blocks bonded together by cementitious material, and said leaves being laterally spaced from each other to provide a cavity therebetween; a frame having sides and being positioned with its sides in close juxtaposition to ends of said walls, and damp proof course elements positioned at least between said frame sides and said ends of said walls, each of said damp proof course elements comprising an integral strip of plastics material along its frame side with corrosionresistant, liquid-impermeable properties, each strip being of constant cross-section throughout its length, each strip having a first longitudinal part and a second longitudinal part, said first part of said each strip engaging between its frame side and at least one of said leaves of its wall end, said second part of said each strip bridging the end of said cavity between said leaves of its wall end, said each strip further having a cavity entering part comprising a pair of laterally spaced walls extending into said cavity, and keying means securing said elements to said walls.
 2. A structural assembly according to claim 1 wherein at least one longitudinal portion of each of said damp proof course elements adjacent its wall has an undercut recess along its length facing its wall to provide said keying means for securing said each element to its wall.
 3. A structural assembly according to claim 1, wherein each said part of said damp proof element engaging between said frame side and said wall is pierced by fixing devices securing said damp proof element to said frame.
 4. A structural assembly according to claim 1, wherein a recess is formed in each said damp proof course element along the length of said part of said damp proof element engaging between said frame side and said wall to provide a keying formation for securing said element to said wall.
 5. A structural assembly according to claim 4, wherein said longitudinally extending recess is dovetail shaped in cross-section.
 6. A structural assembly according to claim 1, wherein a recess is formed in each said damp proof course element along the length of at least one of said laterally spaced walls thereof to provide a keying formation for securing said element to said wall.
 7. A structural assembly according to claim 6, wherein said longitudinally extending recess is dovetail shaped in cross-section.
 8. A structural assembly according to claim 1, wherein said bridging part is connected at opposite ends to adjacent ends of said laterally spaced walls, and the other ends of said laterally spaced walls are spaced to define with said bridging part a substantially U-shaped intermediate configuration in said strip.
 9. A structural assembly according to claim 1, wherein said damp proof course elements are extruded strips.
 10. A structural assembly according to claim 1, wherein said first part of each strip comprises a firSt flange extending along one side edge of the strip in sealing disposition between said frame and the outer end of said one leaf, said second part of said strip comprises a web laterally bridging the end of the cavity between said leaves, and said cavity entering part comprises a pair of laterally spaced walls projecting in the same direction from said web and extending into said cavity and a second flange extending along the other side of said strip sealingly engaging the outer end of the other of said leaves.
 11. The structural assembly defined in claim 10, wherein one of said laterally spaced walls is formed with an undercut recess to provide anchorages for detachable wall ties at any position along the length of said strip.
 12. The structural assembly defined in claim 10, wherein said first flange and said web are substantially parallel and said first flange is formed with oppositely facing longitudinal recesses, one recess opening in the same direction that said laterally spaced walls project and the other opening toward the frame engaging side.
 13. The structural assembly defined in claim 10, wherein said web is formed on the side facing the interior of said cavity with moisture trap grooves. 